Motion transmitters



ep v9, 1958 A. FOSTER 2,850,908

MOTION TRANSMITTERS Filed Feb. 11, 1958 Inventor flaw/6mm 2,850,908 MOTIQN TRANSMKTTERS Alan Foster, Croydon, liingtand, assignor to Powers- Samas Accounting Machines Limited, London, England, a British company This invention relates to motion transmitters and in particular to a transmitter which is adapted to transmit reciprocatory movement from a continuously rotatable driving member.

Basically the invention is concerned with a motion transmitter in which an electrically conductive band looped round a continuously rotatble driving member is movable lengthwise by the driving member due to electrostatic force applied between the band and an intermediate element engaged thereby and carried by the driving member for rotation therewith. Such a transmitter utilizes the well-known Iohnsen-Rahbek effect the theoretical and practical considerations of which are carefully considered in a paper by Miss Audrey D. Stuckes under the title Some theoretical and practical considerations of the Johnsen-Rahbek effect, Proceedings 1. E. E., vol. 103, part B, No. 8, March 1956, pages 125 to 131.

As the result of the tests described in the said paper the conclusion reached was that, owing to the existence of problems, particularly wear and heat generation, to which no adequate solution could be foreseen, an electrostatic motion transmitter involving a continuously rotatable driving member was not a practical proposition. The present invention deals with the problems of wear and heat generation and so minimises them that there is provided a commercially practicable electrostatic motion 2,5,998: Patented Sept. 9, 1%58 "ice lengthwise movement thereof as described in United States Patent specification No. 2,674,652. During an imprinting operation the impresison-receiving material is located between a platen 3 and a carbon ribbon 4 or other similar transfer media.

Imprinting is effected by a plurality of styluses, only one of which is shown in the drawing, each stylus being arranged to effect the definition of a character independently of the others. The styluses consist of wire-like ele ments arranged in side-by-side relation and the marking ends 5 thereof are engaged by a bar 6 which is arranged to reciprocate the marking ends of the styluses in a straight-line path at right-angles to the direction of movement of the impression-receiving material over the platen. Reciprocation of the bar 6 is eifected in any suitable manner, and the amplitude of reciprocation determines one maximum dimension of the characters formed. The other maximum dimension of the characters to be formed is determined by the rate of movement of the impression-receiving material during character definition. Each stylus is urged to the inactive position thereof by a spring 7 and imprinting is effected, in the known manner, by axial or lengthwise movement of the stylus against the action of its spring 7.

The axial movement of the stylus is controlled by electrical pulses transmitted from an electrical pulse generatransmitter capable of being used to convert rotary mo tion into reciprocating motion.

In the investigations mentioned above use was made of a semi-conductor but in carrying the present invention into effect use may be made of an intermediate element which may be a semi-conductor or which may be a dielectric.

According to the present invention a motion transmitter in which an electrically conductive band looped round a continuously rotatable driving member is movable lengthwise by the driving member due to electrostatic force applied between the band and an intermediate element engaged thereby and carried by the driving member for rotation therewith is characterised in that a pivoted lever has arms of unequal length disposed on opposite sides of the pivot therefor and the ends of the band are connected one to each of the said arms. so that on lengthwise movement of the band by the driving member tension inlthe band portion connected to the shorter arm or the lever is relieved thereby to minimise wear and heating at the position at which maximum friction would normally occur between the band and the intermediate element.

In order that the invention may be clearly understood one embodiment thereof will now be described, by way of example, with reference to the accompanying diagrammatic drawing which illustrates a motion transmitter whereby a continuously rotatable driving member is arranged to eifect reciprocation of a stylus.

Referring to the drawing, the definition of characters on impression-receiving material 1 is effected by dots formed by styluses 2 during lateral reciprocation and tor Swhich may be of any suitable form adapted to produce electrical pulses according to the characters to be defined and the outputs from the generator are controlled by a decoding device, not shown, connected with a record sensing device and an accumulator also not shown.

Axial movements are transmitted to the stylus by an electrically conductive band 9, for example a band of stainless steel, which is looped round a continuously rotatable driving member which includes a shaft in rotatable by an electric motor, not shown. An electrically conductive liner ill, for example a silver liner, is connected to the shaft 10, as by flanged bosses 12 at opposite ends of the liner, to be rotatable with the shaft and in effect to form part of the driving member. Betweenthe band 9 and the liner 11 there extends an intermediate element 13 which is engaged by the band. The intermediate element 13 may be madeof a dielectric material orof a material which is a semi-conductor. An example of a suitable dielectric material is barium titanate, or barium titanate which includes a small percentage of strontium titanate, such dielectric materials being hereinafter and in the appended claims referred to as barium titanate. An example of a suitable material which is a semi-conductor is chemically treated magnesium orthotitanate. I, I

The intermediate element 13 is carried by the driving memberltl, 11 to be rotatable therewith and conveniently consists of I a cylinder the outer, periphery of which is polishedto betas smooth as possible, and the liner 11 is caused by a suitable adhesive, to adhereto the interior of the cylinder. If. the pulses from the generator are appliedto the shaft 10 the end faces of the cylinder are silvered in continuation ofthe liner so that the pulses are transmitted to. the liner by wavof the shaft and bosses 12.

, The surface resistivity of the peripheral portion of the cylinder 13 which is engaged bythe band 9 is retained by efiec'ting lubrication thereof by a material selected as suitable to achieve this result. As shown in the drawing, lubrification is effected by a pad 14 of polytetrafluoroethylene which is urged by a spring 15 to be in continuous engagement with the peripheral surface of the cylinder.

As will be understood, the position at which maximum friction, and thus wear and heating, will occur is at about the position F and to minimise friction at this position and so tend further to preserve the surface resistivity of the cylinder the ends of the band 9 are connected to a lever plvoted at 16 and having arms 17, 18 of unequal length. As shown in the drawing the end portions of the band are substantially parallel one to the other and the pivot 16 is offset by distance D from the axis of rotation of the driving member 10, 11 so that the lever arm 17 is shorter than arm 18.

Thus when the band 9 is electrostatically locked to driving member 10, 11 as described below the band portion connected to lever arm 18 rocks the lever clockwise about pivot 16 so relieving tension in the band portion connected to lever arm 17 and minimising friction at position F while permitting lengthwise movement of the band to be transmitted to the stylus 2 through an electrically insulated pad 19 carried by the arm 17.

The band 9 is electrically connected with the pulse generator 8 by a brush 20 and electrical lead 21 and the liner 11 is connected to the generator 8 by a brush 22 and lead 23.

In operation of the device, the driving member 10, 11 together with the cylinder 13 is rotated continuously by a motor, not shown, or if desired from the main drive of the machine, with a velocity, which may, for example, be of the order of from 150 to 500 R. P. M., although it is thought that lower velocities may be used. Any tendency for the band to be moved with the cylinder, before electrostatic locking of the band to the cylinder, is overcome by the spring 7 which also restores the band when a pulse applied across liner 11, intermediate element 13, and band 9 ceases to be operative.

The circuit is energized by a voltage pulse generated by the generator 8 and the voltage pulse is developed across the output impedance of the generator, which may be a resistor 24. The electrostatic force applied between the band 9 and the portion of the cylinder 13 engaged thereby causes locking of the band to the cylinder so that the band is caused to move lengthwise therewith and efiect lengthwise movement of the stylus 2, as described above, so that the marking end of the stylus causes a dot to be marked on the impression-receiving material 1.

On de-energisation of the circuit the output impedance- 24 acts as a discharge shunt so that the spring 7 acts to restore the stylus and band to the starting positions thereof.

In embodiments of the invention which have been operated in practice, the cylinder has a thickness of 0.125 inch, the outside diameter of the cylinder is 1 inch, and the cylinder is rotated at between 150 and 500 R. P. M. The apparatus is operated by pulses having a positive peak value in the range of 50 v. to 200 v., and the current flowing during activation of the device is of the order of 500 micro-amperes. If the cylinder is made of barium titanate, as described above, it has a dielectric constant of 1,200 but this may be increased to 3,000 to 5,000 by the use of suitable additives such as strontium titanate, as mentioned above. 7

Although in the foregoing description the invention has been described as transmitting motion to a reciprocable stylus it will be understood that a motion transmitter as described herein can be used for a number of purposes and that, in particular, having regard to the art of record controlled statistical machines, such a transmitter can be adapted to eifect the setting of set bars of a punch unit,-

or to effect the operation of the punches of a punch unit.

I claim: 1. A motion transmitter in which an electrically con.- ductive band looped round a continuously rotatable driving member is movable lengthwise by the driving member due to electrostatic force applied between the band and an intermediate element engaged thereby and carried by the driving member for rotation therewith, characterised in that a pivoted lever has arms of unequal length disposed on opposite sides of the pivot therefor and the ends of the band are connected one to each of the said arms so that on lengthwise movement of the band by the driving member tension in the band portion connected to the shorter arm of the lever is relieved thereby to minimise wear and heating .at the position at which maximum friction would normally occur between the band and the intermediate element.

2. A motion transmitter according to claim 1, wherein the pivot for the lever is offset from the axis of rotation of the driving member.

3. A motion transmitter according to claim 1, wherethe intermediate element is formed from a dielectric material such as barium titanate.

4. A motion transmitter according to claim 1, wherein the intermediate element is formed from a semi-conductor such as chemically treated magnesium orthotitanate.

5. A motion transmitter comprising a continuously rotatable driving member, an electrically conductive band looped round the driving member, an intermediate element formed from a dielectric material and carried by the driving member for rotation therewith and engagement by said band, and a pivoted lever having arms of unequal length disposed on opposite sides of the pivot for the lever, said band having the opposite ends thereof connected one to each of said arms so that on lengthwise movement of the band by the driving member tension in the band portion connected to the shorter arm of the lever is relieved thereby to minimise wear and heating at the position at which maximum friction would normally occur between the band and the intermediate element.

6. A motion transmitter according to claim 5, wherein the dielectric material is barium titanate.

7. A motion transmitter comprising a continuously rotatable driving member, an electrically conductive band looped round the driving member, an intermediate element formed from a semi-conductor and carried by the driving member for rotation therewith and engagement by said band, and a pivoted lever having arms of unequal length disposed on opposite sides of the pivot for the lever, said band having the opposite ends thereof connected one to each of said arms so that on lengthwise movement of the band by the driving member tension in the band portion connected to the shorter arm of the lever isrelieved thereby to minimise wear and heating at the position at which maximum friction would normally occur between the band and the intermediate element.

8. A motion transmitter according to claim7, wherein the semi-conductor comprises chemically treated magnesium orthotitanate.

References Cited in the file of this patent UNITED STATES PATENTS 1,631,764 Ruben June 7, 1927 2,148,482 Lorenz Feb. 28, 1939 2,630,512 Rahbek Mar. 3, 1953 FOREIGN PATENTS 533,368 France Dec. 8, 1921 

